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Cooperative Extension Service, University of 

 Illinois College of Agriculture in Cooperation With 



the Illinois Natural History Survey and U.S.D.A. 



FOR IMMEDIATE RELEASE July 22, 1966 



INSECT SURVEY BULLETIN NO. lU 



This fourteenth weekly bulletin on the general insect situation in Illinois 

 (fruit insects excepted), prepared by entomologists of the University of Illinois 

 College of Agriculture, Illinois Natural History Survey and cooperating agencies, 

 reports general trends in insect activity and suggests abbreviated control measures. 

 Each individual should check his own fields to determine local conditions. 



Present Farm Insect Problems 



Emergence of European corn borer moths has reached its peak in the area 

 south of a line from Harrisburg to Carbondale (Highway 13) > and egg laying is pro- 

 gressing rapidly. Moths were abundant this week as far north as Highway 50 from 

 Lawrenceville to St. Louis, and more than 80 percent of the first -generation borers 

 had pupated. Moth emergence in this area will reach a peak this week (week of July 25) 

 and egg laying will progress rapidly. 



In central Illinois, pupation ranges from 50 to 75 percent. Some moth emer- 

 gence has occurred, but the peak will not be reached for about another 10 days. 



Pupation of first-generation corn borers has just begun in north-central 

 and northern Illinois. Thus moth emergence and egg laying will not occur in this 

 area until about August 10. 



The general picture for second-generation corn borer in Illinois is not 

 good, but neither is it devastating. In general, 1 to 2 percent of the fields of corn 

 will have three or more mature corn borers per plant by October 1. This number indi- 

 cates a loss of 1 to 2 percent in yield in these fields. However, in a few areas as 

 many as 33 percent of the fields may have an average of three or more borers per 

 stalk by October 1, and some individual fields may lose 5 to 10 percent in yield. 



To decide whether or not to apply an insecticide, count egg masses per 

 plant. If the average is one or more per plant, applications may be profitable. Use 

 1 l/2 pounds of carbaryl (Sevin) or 1 pound of diazinon per acre as granules, applied 

 by air or ground equipment. Sprays applied by ground machines will be as effective 

 as granules in borer control, but sprays applied by airplane will be somewhat less 

 effective. 



Northern corn rootworm adults are now present in numbers throughout the 

 state. They are numerous in fields where corn has been grown consecutively for three 

 or more years. Although these green beetles can be found in southern Illinois corn- 

 fields, they become more noticeably numerous as you go northward in the state. In the 

 northern two to four tiers of counties, they are quite abundant. 



These beetles feed on silks. If pollination has not occurred, kernel set 

 can be affected. But if pollination has occurred, then large numbers of these beetles 

 feeding on silks will do no damage. If pollination is just beginning and there are 

 10 or more beetles per ear, or silking has not started and there are 10 or more beetle: 

 per plant, it may be profitable to apply one pound of carbaryl (Sevin) per acre. 



